Image capturing device

ABSTRACT

An image capturing device is provided. The image capturing device includes an image sensing circuit, a determination circuit and an output circuit. The image sensing circuit is utilized for capturing a first test image at a first time point and capturing a second test image at a second time point. The determination circuit is utilized for calculating a first image feature value associated with a color value of the first test image and a second image feature value associated with a color value of the second test image, calculating a difference value between the first image feature value and the second image feature value and comparing the difference value with a threshold value to generate a determination result. The output circuit is utilized for outputting the images generated by the image capturing device according to the determination result.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.15/603,430, filed on May 23, 2017 and entitled “IMAGE OUTPUT METHOD ANDIMAGE CAPTURING DEVICE”, which is included in its entirety herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an image capturing device, and moreparticularly, to an image capturing device capable of improving thesecurity of image data.

2. Description of the Prior Art

With the development of technology and progress of industry, digitalcameras have been widely utilized in all kinds of electronic devices,such as laptops, tablets, desktops, mobile phones, wearable devices,smart TVs and so on. Since the electronic devices have ability toconnect to the Internet, users utilize the digital cameras mounted onthe electronic devices to take photos and share the photos to otherelectronic devices via the Internet. However, the electronic deviceswith the ability to connect to the Internet are easy to be invaded byhackers via remote control, so as to manipulate the cameras, peep orsteal the images taken by the camera, thus threatening the privacy andsecurity of the users. Therefore, there is a need for improvement.

SUMMARY OF THE INVENTION

Therefore, the present invention primarily provides an image outputmethod and an image capturing device, which is capable of improving thesecurity of image data to solve the above mentioned problems.

The present invention discloses an image capturing device, comprising:an image sensing circuit, for capturing a first test image at a firsttime point and capturing a second test image at a second time point; adetermination circuit, for calculating a first image feature value ofthe first test image and a second image feature value of the second testimage, calculating a difference value between the first image featurevalue and the second image feature value, and comparing the differencevalue with a threshold value to generate a determination result, whereinthe first image feature value of the first test image is associated witha color value of the first test image and the second image feature valueof the second test image is associated with a color value of the secondtest image; and an output circuit, for outputting the images generatedby the image capturing device according to the determination result;wherein the determination result indicates outputting the imagesgenerated by the image capturing device when the difference value isgreater than the threshold value, and the output circuit accordinglyoutputs the images generated by the image capturing device.

The present invention further discloses an image capturing device,comprising: an image sensing circuit, for capturing a first test imageat a first time point and capturing a second test image at a second timepoint; a determination circuit, for calculating a first image featurevalue of the first test image and a second image feature value of thesecond test image, calculating a difference value between the firstimage feature value and the second image feature value, and comparingthe difference value with a threshold value to generate a determinationresult, wherein the first image feature value of the first test image isassociated with a brightness value of the first test image and thesecond image feature value of the second test image is associated with abrightness value of the second test image; and an output circuit, foroutputting the images generated by the image capturing device accordingto the determination result; wherein the determination result indicatesoutputting the images generated by the image capturing device when thedifference value is greater than the threshold value, and the outputcircuit accordingly outputs the images generated by the image capturingdevice.

The present invention further discloses an image capturing device,comprising: an image sensing circuit, for capturing a first test imageat a first time point and capturing a second test image at a second timepoint; a determination circuit, for calculating a first image featurevalue of the first test image and a second image feature value of thesecond test image, calculating a difference value between the firstimage feature value and the second image feature value, and comparingthe difference value with a threshold value to generate a determinationresult, wherein the first image feature value of the first test image isassociated with a focal distance of the first test image and the secondimage feature value of the second test image is associated with a focaldistance of the second test image; and an output circuit, for outputtingthe images generated by the image capturing device according to thedetermination result; wherein the determination result indicatesoutputting the images generated by the image capturing device when thedifference value is greater than the threshold value, and the outputcircuit accordingly outputs the images generated by the image capturingdevice.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an image capturing deviceaccording to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a procedure according to anembodiment of the present invention.

FIGS. 3-5 are schematic diagrams illustrating different proceduresaccording to alternative embodiments of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram illustrating animage capturing device 10 according to an embodiment of the presentinvention. The image capturing device 10 can be utilized in all kinds ofelectronic devices, such as notebooks, tablets, desktops, mobile phones,wearable devices, smart TVs, but not limited thereto. The imagecapturing device 10 includes an image sensing unit 102, a determinationunit 104 and an output unit 106.

The image sensing unit 102 is utilized for capturing images. The imagesensing unit 102 can be a charge-coupled device (CCD) sensor, acomplementary metal oxide semiconductor (CMOS) sensor, or other imagesensors. The image captured by the image sensing unit 102 can be rawimages. The image captured by the image sensing unit 102 can beoutputted directly to other external devices. The image captured by theimage sensing unit 102 can also be provided to an image signal processor(ISP) of the image capturing device 10, such that the image signalprocessor handles corresponding image processing procedure of thecaptured image and outputs for consequent application. For example,image processing procedure executed by the image signal processor can beimage format transformation, auto white balance (AWB), auto exposure(AE), auto focus (AF), contrast adjustment, saturation adjustment, noiseelimination, interpolation, edge enhancement and the like, but notlimited thereto. The image sensing unit 102 can capture imagesconsecutively. For example, the image sensing unit 102 captures testimages in a test mode and captures relative images in a normal mode. Inthe test mode, the image sensing unit 102 captures a first test image ata first time point and a second test image at a second time point.

The determination unit 104 is used for calculating a first image featurevalue of a first test image and a second image feature value of a secondtest image. And the determination unit 104 determines whether to outputimages generated by the image capturing device 10 according to the firstimage feature value of the first test image and the second image featurevalue of the second test image, and accordingly generates adetermination result. The output unit 106 outputs the images generatedby the image capturing device 10 according to the determination resultgenerated by the determination unit 104. In an embodiment, at least oneof the determination unit 104 and the output unit 106 can be implementedby an image signal processor.

In brief, the image capturing device 10 of the present invention candetermine whether to output the images generated by the image capturingdevice 10 according to image feature values of the captured images atdifferent time points. That is, after determination and authenticationof the determination unit 104 and the output unit 106, the imagesgenerated by the image capturing device 10 can be outputted, so as toprovide a security control procedure of image data access. As such, theinvention can effectively prevent hackers from stealing or peeping theimages generated by the image capturing device 10 via remote control,and therefore, improving security of image data.

For an illustration of the operations of the image capturing device 10,please refer to FIG. 2, which is a schematic diagram illustrating aprocedure 20 according to an embodiment of the present invention. Theprocedure 20 includes the following steps:

Step S200: Start.

Step S202: Capture the first test image at the first time point andcapture the second test image at the second time point.

Step S204: Calculate the first image feature value of the first testimage and the second image feature value of the second test image.

Step S206: Determine whether to output the image generated by the imagecapturing device according to the first image feature value of the firsttest image and the second image feature value of the second test image.

Step S208: End.

According to the procedure 20, the present invention can control whetherto output the images based on the images captured by the image sensingunit 102 for improving the security of the image data. When the imagecapturing device 10 receives image access requests or before the imagecapturing device 10 is ready to output the images, first, in Step S202,the image capturing device 10 enters a test mode, and the image sensingunit 102 captures a first test image at a first time point and capturesa second test image at a second time point. For example, the second timepoint is after the first time point. A time interval between the firsttime point and the second time point can be determined according tosystem requirements. For example, the time interval between the firsttime point and the second time point is 30 microseconds (ms). Foranother example, the time interval between the first time point and thesecond time point is 5 seconds(s).

In Step S204, the determination unit 104 calculates a first imagefeature value of the first test image and a second image feature valueof the second test image. For example, the first image feature value ofthe first test image can be a brightness value, a color value, a focaldistance (focal length) or any other image feature values associatedwith the first test image. The second image feature value of the secondtest image can be a brightness value, a color value, a focal distance orany other image feature values associated with the second test image.

In Step S206, the determination unit 104 determines whether to outputthe images generated by the image capturing device 10 according to thefirst image feature value of the first test image and the second imagefeature value of the second test image, and accordingly generates adetermination result. The determination unit 104 can calculate an imagedifference value between the first image feature value and the secondimage feature value. For instance, the determination unit 104 cansubtract the second image feature value from the first image featurevalue to calculate a difference value between the first image featurevalue and the second image feature value. As such, the calculateddifference value is the image difference value between the first imagefeature value and the second image feature value. For another example,the determination unit 104 can calculate an absolute difference betweenthe first image feature value and the second image feature value, andthe absolute difference is the image difference value between the firstimage feature value and the second image feature value. As such, theimage difference value represents a variation between the first testimage at the first time point and the second test image at the secondtime point. Then, the determination unit 104 compares the imagedifference value with a threshold and generates the determination resultaccordingly. For example, when the image difference value is greaterthan the threshold, the determination result indicates to output theimages generated by the image capturing device 10. When the imagedifference value is equal to or smaller than the threshold, thedetermination result indicates not to output the images generated by theimage capturing device 10.

Furthermore, the output unit 106 outputs the images generated by theimage capturing device 10 according to the determination resultdetermined by the determination unit 104. In an embodiment, when thedetermination result indicates to output the images generated by theimage capturing device 10, the output unit 106 outputs the imagesgenerated by the image capturing device 10 to other external devices orother devices, wherein the images generated by the image capturingdevice 10 includes at least one of test images captured by the imagesensing unit 102 in the test mode, images captured by the image sensingunit 102 in the normal mode, images processed by the image processor. Inother words, the output unit 106 can output the test images captured bythe image sensing unit 102 of the image capturing device 10 in the testmode and/or output the images captured by the image sensing unit 102 ofthe image capturing device 10 in the normal mode. Or, the output unit106 can output the images processed by the image processor of the imagecapturing device 10. Therefore, after the determination andauthentication procedure of the procedure 20, if the determinationresult indicates to output the images generated by the image capturingdevice 10, the image capturing device 10 performs image output procedurenormally.

In an embodiment, when the determination result indicates not to outputthe images generated by the image capturing device 10, the output unit106 will not perform any operation. In such a situation, the imagesgenerated by the image capturing device 10 will not be outputted andprovided to other devices. For example, when the determination resultindicates not to output the images generated by the image capturingdevice 10, the output unit 106 can output (or control a display deviceto display) a monochrome image, for instance, a black image or a whiteimage, to indicate not allowable to access the images generated by theimage capturing device 10. That is, in this situation, if thedetermination result indicates not to output the images generated by theimage capturing device 10, the image capturing device 10 will not beallowed to perform the image output procedure normally.

On the other hand, after the determination unit 104 generates thecorresponding determination result, the image capturing device 10 caninform a user whether the images generated by the image capturing device10 can be outputted (or not) by an alarming unit (not illustrated in thefigure). For example, the alarming unit can generate alarm signals (viaall kinds of ways, e.g., words, voices, lights or vibration) to informthe user.

Please refer to FIG. 3, which is a schematic diagram illustrating aprocedure 30 according to an embodiment of the present invention. Theprocedure 30 includes the following steps:

Step S300: Start.

Step S302: Capture the first test image and the second test image.

Step S304: Calculate the brightness value associated with the first testimage and the brightness value associated with the second test image.

Step S306: Calculate the image difference value between the brightnessvalue associated with the first test image and the brightness valueassociated with the second test image.

Step S308: Determine whether the image difference value is greater thanthe threshold; if yes, perform the Step S310; if no, perform the StepS312.

Step S310: Output the image.

Step S312: Not output the image.

According to the procedure 30, in Step S302, when the image capturingdevice 10 receives image access requests or before the image capturingdevice 10 is ready to output the images, the image capturing device 10enters a test mode, and the image sensing unit 102 captures a first testimage at a first time point and captures a second test image at a secondtime point.

In Step S304, the determination unit 104 calculates the brightness valueassociated with the first test image and the brightness value associatedwith the second test image. The pixel brightness value of the first testimage can be an average brightness value of pixels of at least a portionof the first test image. The brightness value of the second test imagecan be an average brightness value of pixels of at least a portion ofthe second test image. In detail, the determination unit 104respectively detects the pixel brightness value of each pixel of atleast a portion of the first test image, and calculates an average ofbrightness values of all pixels of the at least a portion of the firsttest image, and the calculated result is the brightness value associatedwith the first test image. Similarly, for the second test image, thedetermination unit 104 respectively detects the pixel brightness valueof each pixel of at least a portion of the second test image andcalculates an average of brightness values of all pixels of at least aportion of the second test image, and the calculated result is thebrightness value associated with the second test image.

For example, assume that a first region of the images captured by theimage sensing unit 102 usually corresponds to a head region of the userwhen using the image capturing device 10. The determination unit 104 canrespectively detect the pixel brightness value of each pixel of thefirst region of the first test image and the second test image. Andthen, the determination unit 104 calculates the average pixel brightnessvalue of all pixels of the first region of the first test image toobtain the brightness value associated with the first test image, andcalculates the average pixel brightness value of all pixels of thesecond region of the second test image to obtain the brightness valueassociated with the second test image.

For example, calculation of the whole region of the image is alsoavailable. The determination unit 104 can respectively detect thebrightness value of each pixel of the first test image and the secondtest image. After that, the determination unit 104 calculates an averageof brightness values of all pixels of the first test image to obtain thebrightness value associated with the first test image, i.e. taking thecalculated average value as the brightness value associated with thefirst test image. The determination unit 104 calculates an average ofbrightness values of all pixels of the second test image to obtain thebrightness value associated with the second test image, i.e. taking thecalculated average value as the brightness value associated with thesecond test image.

In Step S306, the determination unit 104 calculates an image differencevalue between the brightness value associated with the first test imageand the brightness value associated with the second test image. Forexample, the determination unit 104 can subtract the brightness valueassociated with the second test image from the brightness valueassociated with the first test image, so as to calculate a differencebetween the brightness value associated with the first test image andthe brightness value associated with the second test image. In thissituation, the calculated result is the image difference value betweenthe brightness value associated with the first test image and thebrightness value associated with the second test image. The calculatedimage difference value can show a variation between the first test imageand the second test image. For example, the determination unit 104 cancalculate an absolute difference between the brightness value associatedwith the first test image and the brightness value associated with thesecond test image, and the calculated result is the image differencevalue between the brightness value associated with the first test imageand the brightness value associated with the second test image.

Since an object remains stationary in the images, neighboring framesusually do not exhibit any significant variation, so that the imagedifference value is usually small. When the object is moving in theimages, the image difference value will be larger. Moreover, the user'sbody usually moves slightly or slenderly and is not completelystationary when the user is in shooting range of the image capturingdevice 10. Therefore, in Step S308, the determination unit 104 cancompare the image difference value calculated in Step S306 with athreshold to generate a determination result. For example, when theimage difference value is greater than the threshold, this means thatthe user is in the shooting range of the image capturing device 10 andthe user is using the image capturing device 10. As a result, thedetermination result indicates to output the images generated by theimage capturing device 10. The output unit 106 accordingly outputs theimages generated by the image capturing device 10 (Step S310). On theother hand, when the image difference value is smaller than or equal tothe threshold, this means that the user is not in the shooting range ofthe image capturing device 10. As such, the determination resultindicates not to output the images generated by the image capturingdevice 10. The output unit 106 will not output any image generated bythe image capturing device 10, or the output unit 106 controls a displaydevice to display a black image (Step S312). In other words, the presentinvention can determine whether to output the images generated by theimage capturing device 10 according to the variation of brightness ofthe images, and effectively improve the security of image data access.

Besides, in an embodiment, the relative operations performed by thedetermination unit 104 in steps S304, S306 and S308, can also beimplemented by an auto exposure module of an image signal processor.

Please refer to FIG. 4, which is a schematic diagram of a procedure 40according to another embodiment of the present invention. The procedure40 includes the following steps:

Step S400: Start.

Step S402: Capture the first test image and the second test image.

Step S404: Calculate the color value associated with the first testimage and the color value associated with the second test image.

Step S406: Calculate the image difference value between the color valueassociated with the first test image and the color value associated withthe second test image.

Step S408: Determine whether the image difference value is greater thanthe threshold; if yes, perform Step S410; if no, perform Step S412.

Step S410: Output the image.

Step S412: Not output the image.

According to the procedure 40, in Step S402, when the image capturingdevice 10 receives image access requests or before the image capturingdevice 10 is ready to output the images. The image capturing device 10enters a test mode, and the image sensing unit 102 captures a first testimage at a first time point and captures a second test image at a secondtime point.

In Step S404, the determination unit 104 calculates the color valueassociated with the first test image and the color value associated withthe second test image. The color value of the first test image can be anaverage of color values of pixels of at least a portion of the firsttest image. The color value of the second test image can be an averageof color values of pixels of at least a portion of the second testimage. The color value can be at least a color component value ofthree-primary colors or component value of other colors. In detail, thedetermination unit 104 respectively detects the color value of eachpixel of at least a portion of the first test image, and calculates theaverage of color values of all pixels of the at least a portion of thefirst test image, so that the calculated result is the color valueassociated with the first test image. Similarly, for the second testimage, the determination unit 104 respectively detects the pixel colorvalue of each pixel of at least a portion of the second test image, andcalculates the average of color values of all pixels of the at least aportion of the second test image, so that the calculated result is thecolor value associated with the second test image.

For example, calculation of blue component value of the whole region ofthe image is also available. The determination unit 104 can respectivelydetect blue component value of each pixel of the first test image andthe second test image. After that, the determination unit 104 calculatesthe average of blue component values of all pixels of the first testimage to obtain the color value associated with the first test image,i.e. taking the calculated average value as the color value associatedwith the first test image. The determination unit 104 calculates theaverage of blue component values of all pixels of the second test imageto obtain the color value associated with the second test image, i.e.taking the calculated average value as the color value associated withthe second test image.

In Step S406, the determination unit 104 calculates an image differencevalue between the color value associated with the first test image andthe color value associated with the second test image. For example, thedetermination unit 104 can calculate a difference or an absolutedifference between the color value associated with the first test imageand the color value associated with the second test image. In thissituation, the calculated result is the image difference value betweenthe color value associated with the first test image and the color valueassociated with the second test image. The calculated image differencevalue can show a color variation between the first test image and thesecond test image.

Therefore, in Step S408, the determination unit 104 can compare theimage difference value calculated in Step S406 with a threshold togenerate a determination result. For example, assume that the bluecomponent value is taken as a calculation basis in Step S404. When theimage difference value is greater than the threshold, this means that ablue or similar color object is approaching the shooting range of theimage capturing device 10. As such, the determination result indicatesto output the images generated by the image capturing device 10. Theoutput unit 106 accordingly outputs the images generated by the imagecapturing device 10 (Step S410). On the other hand, when the imagedifference value is smaller than or equal to the threshold, this meansthat no blue or similar color object is approaching the shooting rangeof the image capturing device 10. As such, the determination resultindicates not to output the images generated by the image capturingdevice 10. The output unit 106 will not output any image generated bythe image capturing device 10, or the output unit 106 controls a displaydevice to display a black image (Step S412). That is, the presentinvention can take colors as a key of image output control. For example,when the blue component value is used as the calculation basis and theuser takes a blue card in front of lens of the image sensing unit 102,the output unit 106 will output the images captured by the imagecapturing device 10 after performing the steps of the procedure 40. Inother words, the present invention can determine whether to output theimages generated by the image capturing device 10 according to thevariation of the color value of the images, and effectively improve thesecurity of image data access.

In an embodiment, relative operations performed by the determinationunit 104 in steps S406, S406 and Step S408 can also be implemented by anauto white balance module of an image signal processor.

Please refer to FIG. 5, which is a schematic diagram of a procedure 50according to another embodiment of the present invention. The procedure50 includes the following steps:

Step S500: Start.

Step S502: Capture the first test image and the second test image.

Step S504: Calculate the focal distance associated with the first testimage and the focal distance associated with the second test image.

Step S506: Calculate the image difference value between the focaldistance associated with the first test image and the focal distanceassociated with the second test image.

Step S508: Determine whether the image difference value is greater thanthe threshold; if yes, perform Step S510; if no, perform Step S512.

Step S510: Output the image.

Step S512: Not output the image.

According to the procedure 50, in Step S502, when the image capturingdevice 10 receives image access requests or before the image capturingdevice 10 is ready to output the images. The image capturing device 10enters a test mode, and the image sensing unit 102 captures a first testimage at a first time point and captures a second test image at a secondtime point.

In Step S504, the determination unit 104 calculates the focal distanceassociated with the first test image and the focal distance associatedwith the second test image. The focal distance of the first test imagecan be the focal distance of at least a portion of the first test image.The focal distance of the second test image can be the focal distance ofat least a portion of the second test image. For example, assume that afirst region of the images captured by the image sensing unit 102 istaken as a focal distance evaluation region. The determination unit 104respectively calculates a first focal distance corresponding to thefirst region of the first test image and a second focal distancecorresponding to the first region of the second test image. For example,assume that the whole region of the images captured by the image sensingunit 102 can be taken as the focal distance evaluation region. Thedetermination unit 104 can respectively calculate the first focaldistance corresponding to the first test image and the second focaldistance corresponding to the second test image.

In Step S506, the determination unit 104 calculates an image differencevalue between the first focal distance associated with the first testimage and the second focal distance associated with the second testimage. For example, the determination unit 104 can calculate adifference between the first focal distance associated with the firsttest image and the second focal distance associated with the second testimage. In this situation, the calculated result is the image differencevalue between the first focal distance associated with the first testimage and the second focal distance associated with the second testimage. The calculated image difference value can show a variation of anobject's movement in the first test image and the second test image. Forexample, the determination unit 104 can calculate the absolutedifference between the first focal distance associated with the firsttest image and the second focal distance associated with the second testimage, and the calculated result is the image difference value betweenthe focal distance associated with the first test image and the focaldistance associated with the second test image.

In Step S508, the determination unit 104 can compare the imagedifference value calculated in Step S506 with a threshold to generate adetermination result. For example, when the image difference value isgreater than the threshold, this means that a user is moving, so thatthe determination result indicates to output the images generated by theimage capturing device 10. The output unit 106 accordingly outputs theimages generated by the image capturing device 10 (Step S510). On theother hand, when the image difference value is smaller than or equal tothe threshold, this means that no user exists, so that the determinationresult indicates not to output the images generated by the imagecapturing device 10. And the output unit 106 will not output any imagegenerated by the image capturing device 10 (Step S512). In other words,by the above mentioned method, the invention can automatically recognizewhether the object is moving in the image, and allow image output whendetecting movement variation of the object. That is, the presentinvention can determine whether to output the images generated by theimage capturing device 10 according to the focal distance variation ofthe images, and effectively improve the security of image data access.

Besides, in an embodiment, relative operations performed by thedetermination unit 104 in steps S506, S506 and S508 can also beimplemented by an auto focus balance module of an image signalprocessor.

In summary, in the traditional method, the captured images are directlytransmitted to the display device or the external device for preview orstorage after capturing images. In comparison, the image capturingdevice 10 of the present invention can determine whether to output theimages captured by the image capturing device 10 according to the imagefeature values of the captured images at different time points. That is,the images generated by the image capturing device 10 of the presentinvention can be outputted only after determination and authentication.As such, the present invention can effectively prevent hackers fromstealing or peeping the images generated by the image capturing device10 via remote control and thus enhancing the security of image dataaccess.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An image capturing device, comprising: an imagesensing circuit, for capturing a first test image at a first time pointand capturing a second test image at a second time point; adetermination circuit, for calculating a first image feature value ofthe first test image and a second image feature value of the second testimage, calculating a difference value between the first image featurevalue and the second image feature value, and comparing the differencevalue with a threshold value to generate a determination result, whereinthe first image feature value of the first test image is associated witha color value of the first test image and the second image feature valueof the second test image is associated with a color value of the secondtest image; and an output circuit, for outputting the images generatedby the image capturing device according to the determination result;wherein the determination result indicates outputting the imagesgenerated by the image capturing device when the difference value isgreater than the threshold value, and the output circuit accordinglyoutputs the images generated by the image capturing device.
 2. The imagecapturing device of claim 1, wherein the difference value is an absolutedifference between the first image feature value and the second imagefeature value.
 3. An image capturing device, comprising: an imagesensing circuit, for capturing a first test image at a first time pointand capturing a second test image at a second time point; adetermination circuit, for calculating a first image feature value ofthe first test image and a second image feature value of the second testimage, calculating a difference value between the first image featurevalue and the second image feature value, and comparing the differencevalue with a threshold value to generate a determination result, whereinthe first image feature value of the first test image is associated witha brightness value of the first test image and the second image featurevalue of the second test image is associated with a brightness value ofthe second test image; and an output circuit, for outputting the imagesgenerated by the image capturing device according to the determinationresult; wherein the determination result indicates outputting the imagesgenerated by the image capturing device when the difference value isgreater than the threshold value, and the output circuit accordinglyoutputs the images generated by the image capturing device.
 4. An imagecapturing device, comprising: an image sensing circuit, for capturing afirst test image at a first time point and capturing a second test imageat a second time point; a determination circuit, for calculating a firstimage feature value of the first test image and a second image featurevalue of the second test image, calculating a difference value betweenthe first image feature value and the second image feature value, andcomparing the difference value with a threshold value to generate adetermination result, wherein the first image feature value of the firsttest image is associated with a focal distance of the first test imageand the second image feature value of the second test image isassociated with a focal distance of the second test image; and an outputcircuit, for outputting the images generated by the image capturingdevice according to the determination result; wherein the determinationresult indicates outputting the images generated by the image capturingdevice when the difference value is greater than the threshold value,and the output circuit accordingly outputs the images generated by theimage capturing device.